Real time particle monitor inside of plasma chamber during resist strip processing

ABSTRACT

One aspect of the present invention relates to a system and method for controlling defect formation during a resist strip process. The system includes a reaction chamber comprising a patterned resist layer overlying a semiconductor structure wherein the resist layer is being exposed to a plasma material flowing into the chamber in order to facilitate removing the resist layer from the structure, a plasma-resist particle monitoring system connected to the reaction chamber and programmed to determine a particle count in the reaction chamber during the resist strip process, and a reaction controller coupled to the chamber and to the monitoring system, the reaction controller being programmed to receive particle data from the monitoring system to facilitate determining whether the counted particles in the chamber are within a tolerable limit. The method involves continuing to expose the structure and the chamber to the plasma until an acceptable particle count is obtained.

TECHNICAL FIELD

The present invention generally relates to processing a semiconductorsubstrate. In particular, the present invention relates to controllingdefect formation on a semiconductor wafer during a resist strip processby modifying the resist strip process in order to stabilize and/orreduce defect formation.

BACKGROUND ART

Achieving the objectives of miniaturization and higher packing densitiescontinue to drive the semiconductor manufacturing industry towardimproving semiconductor processing in every aspect of the fabricationprocess. Several factors and variables are involved in the fabricationprocess. For example, at least one and typically more than onephotolithography process may be employed during the fabrication of asemiconductor device. Each factor and variable implemented duringfabrication must be considered and improved in order to achieve thehigher packing densities and smaller, more precisely formedsemiconductor structures.

In general, lithography refers to processes for pattern transfer betweenvarious media. It is a technique used for integrated circuit fabricationin which a silicon slice, the wafer, is coated uniformly with aradiation-sensitive film, the photoresist, and an exposing source (suchas optical light, X-rays, or an electron beam) illuminates selectedareas of the surface through an intervening master template, thephotoresist mask, for a particular pattern. The lithographic coating isgenerally a radiation-sensitized coating suitable for receiving aprojected image of the subject pattern. Once the image is projected, itis indelibly formed in the coating. The projected image may be either anegative or a positive of the subject pattern. Exposure of the coatingthrough the photoresist mask causes a chemical transformation in theexposed areas of the coating thereby making the image area either moreor less soluble (depending on the coating) in a particular solventdeveloper. The more soluble areas are removed in the developing processto leave the pattern image in the coating as less soluble polymer. Theresulting pattern image in the coating, or layer, may be at least oneportion of a semiconductor device that contributes to the overallstructure and function of the device.

Due to the nature of photolithography, the integrity of each layerwithin a semiconductor structure must be maintained throughout thefabrication process in order to obtain a properly formed and fullyoperational device. However, at various stages of a typical fabricationprocess, defects may be introduced onto a layer and may become anindelible part of the completed device. Although some defects may bedetected at or near the completion of fabrication, the repair of suchdefects consumes resources and reduces manufacturing efficiencies. Inaddition, some types of defects may not be detectable, let alonerepairable, thus leading to increased production costs due to waste.

One example of a prominent type of defect is a defect formed whileremoving a photoresist layer from a semiconductor structure. The defectsresult from the interaction between the resist material and othermaterials employed to remove the photoresist layer. The resist and othermaterials form particles which may fill the spatial area on, above,and/or around some portion of the semiconductor structure. Therefore,some of the particles are undesirably deposited onto the structure andthus become defects on the structure.

Conventional end-point detection systems may find these defects,however, the detection of them occurs after the device is substantiallyfabricated. Thus, the conventional detection systems may be problematicfor several reasons. In particular, the defects are perpetuatedthroughout the semiconductor structure, thereby inhibiting proper deviceperformance and function. Hence, there is an unmet need for a systemand/or method to mitigate such defects at an earlier stage in thefabrication process.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

The present invention provides a system and method for controlling theformation of defects in real time while a resist layer is being strippedfrom a semiconductor wafer via a plasma material. In particular, while asemiconductor structure is undergoing a process to remove the resistlayer in a chamber, a particle monitor can be programmed to continuouslycount particles present in and analyze and track the particle countsassociated with the chamber. The particle count relates to a number ofdefects which may adversely affect the structural integrity of thesemiconductor structure.

Thus, as the particle count increases to an amount which is intolerableto the semiconductor structure, a reaction time for the resist stripprocess is modified or extended such that the plasma material maycontinue to react with the particles in the reaction chamber even afterthe resist layer has been substantially removed from the wafer.According to an aspect of the present invention, the continued exposureor overexposure of the particles to the plasma material facilitatesstabilizing the particles (defects) to thereby reduce and/or eliminatethem from the reaction chamber. Once the particle monitor determinesthat an amount of defects which is tolerable to the structure is presentin the chamber, the plasma flow as well as the resist strip process canbe terminated.

One aspect of the present invention relates to a system for controllingdefect formation during a resist strip process. The system includes areaction chamber comprising a patterned resist layer overlying asemiconductor wafer wherein the resist layer is being exposed to aplasma material flowing into the chamber in order to facilitate removingat least a portion of the resist layer from the wafer; a plasma-resistparticle monitoring system operatively connected to the reaction chamberand programmed to determine a count of particles in the reaction chamberduring the resist strip process and to track the particles countedrelative to the flow of the plasma material in real time; and a reactioncontroller operatively coupled to the reaction chamber and to theplasma-resist particle monitoring system, the reaction controller beingprogrammed to receive particle data from the monitoring system tofacilitate determining whether the counted particles in the reactionchamber are within a tolerable limit in order to mitigate defectformation on the semiconductor wafer.

Another aspect of the present invention relates to a method for realtime reduction of defect formation during a resist strip process in areaction chamber. The method involves forming a patterned resist layerover a semiconductor wafer, the patterned resist layer having one ormore openings therethrough; etching the semiconductor wafer through oneor more openings of the patterned resist layer in order to form at leastone feature in the semiconductor wafer; exposing the patterned resistlayer to a plasma material in order to strip at least a portion of theresist layer from the semiconductor wafer; monitoring particles in thereaction chamber while exposing the patterned resist layer to the plasmamaterial; and continue exposing the semiconductor wafer to the plasmamaterial in order to obtain a desired reduction of defects in thechamber.

According to yet another aspect of the present invention, monitoring theparticles within the chamber may provide an indication that the chamberneeds to be cleaned prior to a subsequent wafer process. In particular,one or more aspects of the system and method described above maycommunicate a signal indicating that an average particle count ofparticles in the chamber measured over the course of a resist stripprocess is higher than an acceptable average particle count for areaction chamber. As a result, notification of a relatively dirtychamber may be readily available to a user.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a high level, schematic block diagram of a system forcontrolling defect formation in real time in accordance with an aspectof the present invention.

FIG. 2 illustrates a schematic block diagram of a system for controllingdefect formation in real time in a reaction chamber during a resiststrip process in accordance with an aspect of the present invention.

FIG. 3 illustrates a schematic, cross-sectional view of a semiconductorstructure having at least one feature formed therein in accordance withan aspect of the present invention.

FIG. 4 illustrates a schematic, cross-sectional view of a semiconductorstructure showing at least one feature substantially formed therein inaccordance with an aspect of the present invention.

FIG. 5 illustrates a schematic, cross-sectional view of a semiconductorstructure having at least one feature formed therein undergoing aprocess to strip the photoresist layer therefrom in a reaction chamberin accordance with an aspect of the present invention.

FIG. 6 illustrates a schematic, cross-sectional view of a semiconductorstructure undergoing a process to strip the photoresist layer therefromin a reaction chamber while a plasma particle counter is employed inreal time in accordance with an aspect of the present invention.

FIG. 7 illustrates a schematic, cross-sectional view of a semiconductorstructure undergoing a resist strip process in a reaction chamberwherein the reaction chamber demonstrates an intolerable amount ofparticles in accordance with an aspect of the present invention.

FIG. 8 illustrates a schematic, cross-sectional view of a semiconductorstructure in a reaction chamber in real time after extending a resiststrip process reaction time in accordance with an aspect of the presentinvention.

FIG. 9 illustrates an exemplary graphical plot indicating an inverserelationship between a number of defects in a reaction chamber and anamount of plasma applied over time in a resist strip process inaccordance with an aspect of the present invention.

FIG. 10 illustrates an exemplary method for controlling defect formationduring a resist strip process in real time in accordance with an aspectof the present invention.

DISCLOSURE OF INVENTION

The present invention involves a system and method for controllingand/or reducing defect formation in real time on a semiconductorstructure while the semiconductor structure is undergoing a process toremove a photoresist layer therefrom. More specifically, the presentinvention provides a system and method which can be programmed to extenda resist strip process in order to stabilize particles which arise as abyproduct of the resist strip process. The process may take place in achamber such that the particles are contained within the chamber and canadhere to or rest upon some portion of the semiconductor structureand/or some portion of the chamber. Stabilization of the particleseffectively allows for their removal from the chamber in order tomitigate and/or reduce the number of particles adhering to thestructure.

According to one aspect of the present invention, the particles compriseresist materials and/or plasma materials, or a combination thereof. Forexample, oxygen (O₂) plasma material may be used to strip the resistlayer from the semiconductor structure. As the process continues, thechamber environment includes particles of plasma material as well asparticles of resist material. The particles of these materials mayincrease as more of the resist layer is removed from the semiconductorstructure. Although the chamber can be configured such that a majorityof the particles are evacuated from the chamber, some of the particlesmay not be expelled from the chamber as desired. The particles whichundesirably remain in the chamber during the resist strip process canlikely form into or become defects on the semiconductor structure.

In order to mitigate and/or reduce the presence of these unwantedparticles in the chamber during the resist strip process, one aspect ofthe present invention involves monitoring the particles by counting themand providing the particle count in real time to a particle analyzer.The particle analyzer can determine if the particle count isapproximating a level of defects which is destructive or intolerable bythe semiconductor structure. If and/or when it is determined that theamount of particles (defects) in the chamber are at or near anintolerable level, the resist strip process can be modified. Inparticular, such modification can be in the form of extending the amountof time that the semiconductor structure and the chamber is exposed tothe plasma material. Continued exposure or overexposure of the chamberas well as the semiconductor structure to the plasma facilitatesstabilizing the particles so that they can be evacuated from the chamberas desired, thus leaving either no particles or a tolerable amount ofparticles in the chamber.

The amount of particles tolerable by the semiconductor structure dependson the type of structure and its intended application or use. As soon asthe particle monitor recognizes that the amount of particles has fallento a tolerable number, a termination signal can be communicated to theresist strip process.

Because the system and method of the present invention operate in realtime, a particle monitoring system responsible for tracking, counting,and ascertaining whether too many particles remain in the chamber mayprovide data associated with the particle counts, amounts of plasmamaterial supplied to the chamber, rate of plasma flow, and the like in acontinuous manner. The data may also be plotted as it is obtained by themonitoring system in order to provide a visual aide to a user. Bygraphing the data, it should be apparent to the user that the number ofdefects or particles decreases as the plasma exposure time increases.

The present invention will now be described with respect to an exemplarysemiconductor structure as demonstrated in FIGS. 1–11 below. Theexemplary semiconductor structure is described below as having apatterned resist layer thereon. However, it should be appreciated thatthe resist layer need not be patterned and such is intended to fallwithin the scope of the present invention.

FIG. 1 depicts a system 100 for controlling an amount of particlespresent in a resist reaction chamber 110 in accordance with one aspectof the present invention. The system 100 includes the resist reactionchamber 110 in which a resist strip process is occurring. The resiststrip process involves removing a resist layer from at least a portionof a semiconductor structure using a plasma material. As the resiststrip process continues, particles may form in the chamber 110. Not allof the particles may be expelled from the chamber 110 as desired. Thus,a particle monitoring system 120 may also be included in the system 100.The particle monitoring system 120 counts the particles present in thechamber 110 over the course of the resist strip process. That is, thecounting of the particles occurs in real time as the strip processprogresses. The particle monitoring system 120 is operatively connectedto the chamber 110 in order to count the particles and track the numberof particles counted in relation to a length of time the chamber and thestructure have been exposed to the plasma.

In addition, the particle monitoring system 120 determines whether theparticle count exceeds an amount of defects which the structure cantolerate without experiencing diminished performance and/or function. Ifthe particle count does reach an intolerable number of defects, theparticle monitoring system 120 can communicate the related data and/orinformation to a reaction controller 130. The reaction controller 130 iscoupled to the particle monitoring system 120 as well as to the chamber110 and can instruct the chamber 110 to extend the resist strip processsuch that the chamber continues to receive the plasma material. Theplasma material facilitates stabilizing the particles in order totransform them into a disposable product which can be expelled by thechamber 110. Thus, fewer particles are present in the chamber 110,thereby resulting in fewer defects forming on the structure.

FIG. 2 illustrates a system 200 for reducing defect formation during aresist strip process in real time in accordance with another aspect ofthe present invention. The system 200 includes a chamber 210 in which achamber reaction 215 occurs between a plasma material and a resistmaterial which is to be removed at least in part a semiconductorstructure. The plasma material can be used to remove at least a portionof a patterned resist layer which overlays a semiconductor structure.The reaction that occurs during the resist strip process may yieldundesirable byproducts or particles. The particles may comprise a resistmaterial and/or a plasma material, which when found together canindicate that a reaction between the two materials did not occurproperly. The particles can correspond to defects, and in particular,defects capable of impairing the function of the semiconductorstructure.

In order to mitigate defect formation on the semiconductor structureduring the resist strip process, the system 200 includes a real timeplasma-resist particle monitor 220 connected to the chamber 210 suchthat data from the chamber 210 may be transmitted (solid arrows) to themonitor 220. The particle monitor 220 comprises a particle counter 230which can be programmed to sense and count (dotted arrows) the particlespresent in the chamber 210 on a real time basis so that this data may bepresented to the system 200 and/or to a user for an immediate responseor for immediate use by the system 200 and/or by the user.

The system 200 also includes a particle analyzer 240. The particleanalyzer receives the data from the particle monitor 220, and inparticular, from the particle counter 230, and processes such data inorder to determine whether the particles in the chamber 210 exceed atolerable count. The particle analyzer 240 can determine this bycomparing the particle data to a database 245 of resist strip processparameters which may include tolerable particle counts for various typesof devices. The amount of particles which can be tolerated by thesemiconductor structure depends on the type of structure and the overalltype of device being fabricated at the present time.

The information produced by the particle analyzer 240 can becommunicated to a plasma-resist reaction controller 250. The reactioncontroller 250 regulates and controls the resist strip process reaction215 as it occurs in the reaction chamber 210 via one or more resiststrip process components 260. In particular, the reaction controller 250receives information generated by the analyzer 240. Such information mayindicate whether the most recently obtained particle count is greaterthan a prescribed tolerable amount of particles for the particulardevice being manufactured.

The controller 250 employs this information (feedback 270) by eithercommunicating it to the one or more components 260 or by transforming itinto usable instructions directed to the one or more components 260 forimmediate implementation. Examples of the one or more resist stripprocess components include at least one of plasma type, temperature,pressure, flow rate, exposure time, and power.

Moreover, the system 200 utilizes controlled feedback 270 in order tocommunicate to the one or more components 260 responsible for carryingout the resist strip process to continue the plasma exposure (acomponent) beyond a pre-programmed time limit and/or extend the plasmaexposure time in order to stabilize and reduce the number of particlescounted in the chamber 210.

Therefore, when the controller communicates information indicating thatthe particle count is essentially at an intolerable level, one or morecomponents may be adjusted in order to extend the resist strip processbeyond the pre-set reaction length. In particular, the interior of thechamber 210 including the semiconductor structure may be subjected to aprolonged plasma exposure in order to facilitate an evacuation of theparticles present in the chamber 210. The particle count may increase asmore of the resist layer is removed from the semiconductor structure.Hence, plasma may be supplied to the chamber 210 in order to reduce theparticle count even though the resist layer has been substantiallyremoved from the semiconductor structure. The plasma may be supplied tothe chamber at a constant rate or at increasing rates which are suitableto carry out the present invention without damaging the semiconductorstructure.

A power supply 280 such as a suitable battery or otherwise can be usedto effectively and efficiently operate the system 200.

Turning now to FIG. 3, a partial view of a system 300 for controllingdefect formation during a resist strip process is shown. FIG. 3 depictsa schematic, cross-sectional view of a semiconductor structure 305undergoing a fabrication process by a feature fabrication system 307. Inparticular, the semiconductor structure 305 includes a substrate 310 andat least one material layer 320 which may comprise any one of a metal,non-metal, organic and/or inorganic material, or a combination there of.The structure 305 may also include one or more material layers 320. Theuppermost layer on the structure 305 is a patterned photoresist layer330. The patterned photoresist layer 330 comprises one or more openings340 therethrough which correspond to one or more features to be formedin the underlying layer 320. Examples of the features being formed inthe structure 305 include vias, contacts, plugs, capacitors, trenches,and the like.

As shown in FIG. 3, the feature fabrication system 307 is etching (350)the material layer 320 through the one or more openings 340 of thephotoresist layer 330. The system 300 also includes a plasma-resistparticle counter 360. Because the semiconductor structure 305 has notyet entered a resist strip process phase, the particle counter 360 maysit idle until it is activated or signaled by resist strip processcomponents.

FIG. 4 is similar to the system represented in FIG. 3. A semiconductorstructure 400 has been substantially etched and developed. The structure400 includes a silicon substrate 410, one or more intermediate layers420, and a patterned photoresist layer 430 as the uppermost layer. Thepatterned photoresist layer 430 comprises one or more openings 440 whichhave been transferred to the underlying intermediate layer 420 by somesuitable aspect of a feature fabrication system 450. A plasma-resistparticle counter 460 can remain idle until the semiconductor structure400 is subjected to a process for removing the patterned photoresistlayer 430 therefrom.

FIG. 5 depicts a system 500 for controlling defect formation on asemiconductor structure 505 similar to the structure 400 described inFIG. 4 during a resist strip process. The structure includes a siliconsubstrate 510, one or more intermediate layers 520 which have beensubstantially etched to reveal one or more features therein, and apatterned photoresist layer 530 as the uppermost layer of the structure505. The patterned photoresist layer 530 comprises one or more openings540 which have been transferred to the underlying intermediate layer 520by a feature fabrication system 450 (FIG. 4).

According to FIG. 5, the resist strip process is taking place within areaction chamber 535. That is, the semiconductor structure 505 is housedand held inside of the reaction chamber 535 throughout the resist stripprocess. In order to remove at least a portion of the patterned resistlayer 530 from the semiconductor structure 505, a plasma material 550 isemployed and introduced into the chamber 535 via a valve 555 or relatedtype of controllable flow mechanism. The plasma material 550 maycomprise oxygen, for example.

As shown in FIG. 5, a portion R1 580 of the resist layer 530 has beenstripped away from the structure 505. The resist strip process involvesa reaction between the resist material and the plasma material such thatchemical bonds are disrupted and/or broken such that the resist materialmay be gradually removed from the semiconductor structure withoutcausing damage to the structure. However, some resist material particlesand plasma particles 560 do not properly react together. As a result,they 560 cannot be expelled from the chamber 535 as are the majority ofthe particles. The particles 560 that remain in the chamber correspondto a number of defects 560 which may potentially contaminate thesemiconductor structure 505. For example, the defects 560 may eventuallysettle and/or deposit themselves on the semiconductor structure 505.They may remain there throughout the fabrication process and ultimatelyrender the manufactured device inoperable or substandard for commercialuse.

Since some defects can be tolerated by the semiconductor structure 505(or final device), a plasma-resist particle counter 570 may be employedwhile the resist strip process takes place to monitor 575 a particlecount of the particles 560 present in the chamber 535. Data relating tothe particle count can then be transmitted to a particle analyzer (FIG.2) to determine whether the present particle count exceeds an acceptableor tolerable particle limit for the particular device being fabricated.

FIG. 6 illustrates another aspect 600 of the present invention as theresist strip process progresses along. In particular, a semiconductorstructure 605, which includes a substrate 610, one or more etched layers620 over the substrate and a partially removed resist layer 630 over theetched layer 620, is housed within a reaction chamber 635, in which theresist strip process is taking place.

The resist layer 630 also has one or more openings 640 therethroughwhich extend through the etched layer 620 in order to expose an uppersurface of the substrate 610. The resist layer 630 has been partiallyremoved as indicated by a depth or length R2 680, such that R2 680 isgreater than R1 580 (FIG. 5). Plasma 650 continues to be supplied intothe chamber 635 in order to facilitate the removal of the resist layer630 from the structure 605.

A plasma-resist particle counter 670 similar to the counter 570 of FIG.5 continues to monitor 675 the chamber 635 in order to obtain a count ofparticles 660 undesirably contained in the chamber 635. As can be seenin FIG. 6, more particles 660 remain in the chamber 635 as the resiststrip process progresses and as more of the resist layer 630 is removed.

FIG. 7 illustrates a yet another aspect of the system 700 forcontrolling defect formation during a resist strip process. Inparticular, the system 700 includes a semiconductor structure 705 havinga substrate 710 and an etched layer 720, wherein the etched layer 720includes one or more features 730 formed therein. As a result of theresist strip process, a resist layer similar to the resist layer 630 ofFIG. 6 has been substantially removed from the structure 705. Thesemiconductor structure is housed in a reaction chamber 735 wherein theresist strip process may occur.

A plasma-resist particle counter 740 continues to obtain 745 a count ofparticles 750 present in the chamber 735. Likewise, one or morecomponents (not shown) of the resist strip process continue to performtheir functions until they are instructed to terminate. Instructions tothe components may be provided by a plasma-resist reaction controller755. The plasma-resist reaction controller 755 is operatively connectedto the plasma-resist particle counter 740 (FIG. 2) such that it mayreceive a continuous feed of particle data in real time as the resiststrip process occurs.

Because the particles 750 present in the chamber after the resist layerhas been substantially removed exceed a particle amount which istolerable to the structure 705, plasma 760 continues to flow into thechamber 735 either at a constant rate or at a variable rate. Morespecifically, the controller 755 instructs the resist strip process, andin particular, the plasma component, to remain on for continued flowinginto the chamber 735. The continued plasma flow 760 into the chamber 735and resulting exposure to the structure 705 stabilizes the particles 750such that they are transformed into a form which is expellable by thechamber 735.

FIG. 8 depicts an exemplary system 800 for controlling defect formationduring a resist strip process wherein particles 860 in a chamber 805have been substantially reduced. The chamber also includes a partiallyfabricated semiconductor structure 810 having a silicon substrate 815and an etched layer 820 thereon. The etched layer comprises one or morefeatures 840 formed therein.

As previously discussed, a plasma-resist particle counter 850continuously monitors 855 the chamber 805 in order to ascertain thenumber of particles 860 present in the chamber 805. The particle countis immediately communicated to plasma-resist reaction controller 870. Ifthe particle count exceeds a tolerable level of particles for thespecific device being manufactured, plasma is instructed to continue toflow into the chamber 805 until a particle count falling within thetolerable level is realized by the particle counter 850.

According to FIG. 8, the number of particles 860 remaining in thechamber 805 is substantially lower than as shown in FIGS. 5–7, therebydemonstrating that a required amount of the particles have beensuccessfully evacuated from the chamber 805 as desired. The particlecounter 850 determines that the present number of particles 860 in thechamber 805 is below the intolerable level and thus, the resist stripprocess, and in particular, the plasma component, is terminated.Accordingly, a valve 880 for the plasma has been closed.

FIG. 9 depicts a graphical display 900 of a relationship between anumber of defects or particles 910 and a plasma exposure rate 920 overtime with respect to a resist strip process. In particle, as the resiststrip process begins and progresses, the number of defects present inthe reaction chamber increases 930. However, as the plasma exposure isprolonged or extended beyond what is necessary to strip the resist fromthe semiconductor structure (935), the number of defects decreasesdramatically (940) to a quantity tolerable by the structure (950). Atthis point, the plasma may be terminated immediately and the structuremay proceed to subsequent fabrication stages.

Turning now to FIG. 10, a flow diagram of an exemplary method 1000 ofcontrolling defect formation during a resist strip process, aspictorialized in FIGS. 1–8, is shown. In particular, the method 1000involves monitoring particles present and/or being formed in a chamberin which the resist strip process is taking place. The resist stripprocess removes at least a portion of a photoresist layer from asemiconductor structure or wafer using a plasma material.

Monitoring the particles in the chamber may be accomplished in part bycounting them using a particle counter which has been programmed to besensitive to such particles comprising resist and plasma materials. Theplasma material reacts with the resist material in such a way that theresist material is lifted from the semiconductor structure and expelledfrom the chamber. However, because some resist particles do not reactproperly with the plasma, particles comprising of resist and plasmamaterials float about and/or adhere to portions of the chamber andeventually to exposed portions of the semiconductor structure. Theseparticles become undesirable defects when adhered to the structure. Iftoo many particles (e.g., defects) are present in the chamber, thestructure cannot tolerate them and/or function as needed. Thus, acontinued or over exposure to plasma even after the resist layer hasbeen substantially removed from the semiconductor structure may beemployed in order to stabilize the free-floating particles into a formexpellable by the chamber.

The method 1000 may be accomplished in part by employing a particlemonitoring system. For example, a wafer or semiconductor structure isprepared to undergo the resist strip process (at 1010). In addition, oneor more resist strip parameters may be programmed at 1020. Examples ofthe parameters include any one of plasma type, pressure, flow rate,temperature, power, and time duration. Next, the resist strip process isinitiated in a reaction chamber in order to remove at least a portion ofthe photoresist layer from the semiconductor structure at 1030. At 1040,the particle monitoring system monitors for particles in the chamber.

When particles are detected, a particle counter is employed at 1050 tocount the particles. The particles comprise resist and plasma materialsand/or other materials which arise from the resist strip process. Theparticle counter provides the particle counts in real time to a particleanalyzer and/or reaction controller, either of which determine whetherthe most recent or most current particle count exceeds a tolerable levelof particles for the particular device being made. Because the particlecount is a real time reflection of the chamber, data relating to theparticle count can be generated and communicated to other systemcomponents of the resist strip process in an immediate fashion. After atleast two particle counts have been obtained during the resist stripprocess, an average of the particle counts may be performed at 1052 inorder to determine if the chamber requires a cleaning prior to asubsequent resist strip process. If the average particle count isacceptable at 1054, then an audible, visual and/or electronic signal isprovided to indicate that the chamber is to be cleaned at 1056 prior tothe subsequent resist strip process. On the other hand, if the averageparticle count is acceptable, then another signal can be provided at1058 to indicate that the chamber may continue for use in the subsequentresist strip process.

Referring back to 1050, if the particle count is acceptable at 1060,then the reaction controller instructs one or more components of theresist strip process to terminate the plasma flow and/or the resiststrip process according to the pre-set parameters (at 1070). The methodthen ends at 1075. However, if the particle count is not acceptableand/or tolerable by the semiconductor structure, then the reactioncontroller signals the one or more resist strip process components tomodify the plasma exposure time. For instance, if the particle countobtained after the resist layer has been substantially removed indicatesthat the particles in the chamber are at an intolerable level, thecontroller instructs the plasma flow to continue (at 1080). Terminationof the plasma flow depends on particle counts which are subsequentlyobtained and analyzed. Thus, after the plasma flow is modified, themethod returns to about 1040 where the particles in the chamber aremonitored again and subsequently counted.

Although the invention has been shown and described with respect toseveral aspects, it is obvious that equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of this specification and the annexed drawings. Inparticular regard to the various functions performed by the abovedescribed components (assemblies, devices, circuits, etc.), the terms(including any reference to a “means”) used to describe such componentsare intended to correspond, unless otherwise indicated, to any componentwhich performs the specified function of the described component (i.e.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary embodiments of the invention. In addition,while a particular feature of the invention may have been disclosed withrespect to only one of several embodiments, such feature may be combinedwith one or more other features of the other embodiments as may bedesired and advantageous for any given or particular application.

1. A method for real time reduction of defect formation during a resist strip process in a reaction chamber comprising: forming a patterned resist layer over a semiconductor structure, the patterned resist layer having one or more openings therethrough; etching the semiconductor structure through one or more openings of the patterned resist layer in order to form at least one feature in the semiconductor structure; exposing the patterned resist layer to a plasma material in order to strip at least a portion of the resist layer from the semiconductor structure; monitoring particles in the reaction chamber while exposing the patterned resist layer to the plasma material to provide particle count feedback; and continuously exposing the semiconductor structure to the plasma material in order to obtain a desired reduction of defects in the chamber based on the particle count feedback.
 2. The method of claim 1, further comprising tracking the counted particles relative to the plasma material flowing into the reaction chamber in order to project an end point for the resist strip process.
 3. The method of claim 1, wherein the continued exposure to the plasma material stabilizes the particles in the reaction chamber such that the reduction of defects in the chamber is realized.
 4. The method of claim 1, wherein the particles comprise at least one of a resist material and a plasma material.
 5. The method of claim 1, wherein monitoring the particles in the reaction chamber comprises counting the particles in the chamber and comparing the particles count to a desired particle count that is tolerable by the semiconductor structure.
 6. The method of claim 1, further comprising using a reaction controller to signal one or more resist strip process components coupled to the reaction chamber to continue exposing the semiconductor structure to the plasma material until the particles counted are reduced to at least a desired particle count.
 7. The method of claim 6, wherein the process components comprise at least one of plasma type, temperature, pressure, flow rate, exposure time, and power.
 8. The method of claim 1, wherein the particles counted in the reaction chamber correspond to an amount of defects present in the chamber.
 9. The method of claim 1, wherein the reaction chamber comprises a valve opening in order to permit the plasma to enter the chamber.
 10. The method of claim 1, further comprising terminating the resist strip process when a desired reduction of the particles in the reaction chamber is obtained.
 11. The method of claim 1, wherein the particles in the reaction chamber result from interactions between the plasma material and the resist layer being removed.
 12. The method of claim 1, wherein the intolerable amount of particles in the reaction chamber is predetermined by a user and is dependent upon a desired application of the semiconductor structure.
 13. The method of claim 1, further comprising providing a signal to indicate that the reaction chamber is to be cleaned prior to a subsequent resist strip process.
 14. The method of claim 13, wherein the signal is provided when an average particle count of particles in the chamber measured during a resist strip process is higher than an acceptable average particle count for the chamber. 